Tunnel kiln



Feb. 16,1926. 1,573,543

F. A. J. FITZ GERALD TUNNEL KILN I Filed June 1, 1925 avweuto'c PatentedFeb; 16, 1926.

UNITED STATES PATENT OFFICE.

FRANCIS A. J. GERALD, Oi NIAGARA FALLS, NEW YORK, ASSIGNOR TO HARPERELECTRIC FURNACE CORPORATION, A CORPORATION OF NEW YORK.

TUNNEL KILNZ- Application filed 'June 1, 1925. Serial Molasses.

To all whom, it may concern:

Be it known that I, FRANCIS GERALD, a citizen of the United States,resid ing at- Niagara Falls, in the county of Niagara andState of NewYork, have invented certainnew and useful Improvements in Tunnel Kilns,of which the following is a specification.

p This invention relatesv to tunnel kilns and particularly to animproved kiln wherein the heat wasted is reduced to a minimum.

In the Operation of tunnel kilns it is the practice to convey thematerial or articles to be heattreated through the kiln on trucksor-other carriers, the articles, in general, be ing supported in saggersmounted on refractory supports carried-by trucks. Any heat conveyed tothe refractories supporting the saggers or to the body of thetruck'diminishes the thermal efficiency of the heattreating process,as'this heat serves no useful purpose and is ultimately lost. The higherthe temperature required for the heat-treatment,the greater is the loss,for where this temperature is very" high a considerable thickness ofrefractories must be interposed between the bottom of the lowest sag erand the top of thetruck, and these reti' actories absorb a largequantity of heat .which is wasted. The principal object of the presentinvention is to provide an improved means for supporting the material tobe heat-treated, or the saggers containing such material, from thetruck, which means has high heat-insulating properties and issufiiciently refractory to be unaffected by the highest temperature towhich it is sub- 'jected.

Other objects of my invention will appear vfrom the following,description, taken in connection with the accompanying drawing, whereinFig. 1 shows diagrammatically in transverse section a tunnel kiln, andshows in elevation, partly broken away, a truck and sagger supportembodyingone form of my invention. a

Fig. 2 is a detail view similar to Fig. 1

l ig. 3 is a top plan view of the sagger supporting tray shown in Fig.2.

Fig. 4 is a section taken onthe line a -a I of Fig. 3.-

lteferring to Fig; 1 of the drawing,

A. J. Frrz represents a kiln of heat-insulating material which forms aheating chamber 2, through which tracks 3 carrying the saggers 4 areadapted to be moved. Means, not shown, is

provided for supplying heat to the upper portion of the chamber 2 toheat the articles contained in the saggers'. To reduce the heating ofthe lower portion of the chamber 1 2 and the lower portion of the trucks3, the

walls of the kiln' are thickened at their lower portion, thereby formingshoulders 10, and the upper portions of the trucks are formed wider thanthe lower portions so that the narrow clearance spaces 11 between thetrucks and the walls of the kiln are angular in vertical section andprevent any direct radiation of heat from the upper to the.

the knobs 5 and forms in effect a tray which is filled with refractorymaterial 6 of high heat-insulating properties. The material 6 mayconsist of any suitable refractory of sufficiently high heat-insulatingproperties and will vary with the workingtempera-' ture of the kiln andother special conditions. Thus, if the maximum temperature of thebottonrsagger in the kiln were not more than 900 C. infusorial earth maybe employed. At very high temperatures, where the atmosphere of the kilnis strictly reducing, powdered charcoal may be employed.

If, however, at this high temperature an OXlClIZIIIg' atmosphere exists,some such material as silico-carbide may be used. When silico-carbide isemployed, known as fibrox (descrlbed in Transactions A, E, S, Vol. 27,1915, pp. 267 et seq.) may be employed to advantage. In certain casesthe receptacle at the top of the truck may be filled with a mixture ofhighly refractory material and sawdust or the likc,-and the mixture thenburned at a temperature where the refractory material is sintered so asto that varietyform a porous, highly refractory material which onaccount of its porosity will have very low hcat-comluctivity.

The material 6 being of low .hcat-conductivity, forms a heat-insulatingmedium between the ggers and the body of the truck. T he suppoi tray maybe formed as a separate receptacle placed on or suitably secured to thetop of the truck body. In Fig. 2 I have shown a modification of myinvention in which the saggcrs 16 are supported on a tray 15 which, inturn, is supported and spaced from the top of the truck by uprigl'its14-. The tray 15 may be formed of any suitable retractory material andcomprises thin and rather deep side walls 17 and upwardly extending thinribs 18 and 19. V

I claim:

1. A sagger carrier for use in tunnnel kilns consisting of a metal bodythe top of which is formed as a receptacle, divided refractoryheat-insulating material contained in said receptacle, andsagger-supporting members in said material.

2. A sagger carrier :tor use in tunnel kilns having a receptacle at itstop, charcoal in said receptacle, and thin sagger-sup-- porting membersin said charcoal.

A sagger carrier for use in tunnel kilns having a receptacle at its top,silicocarbide in said receptacle, and thin saggersaid means and soarranged as to form a heat-insulating medium between the saggers on saidcarrier and the body of said carrier.

6.1K tunnel kiln having a chamber, a series of abutting carriers in saidchamber, said carricrshaving body portions whose sides lie closelyadjacent to the sidewalls of said chamber, whereby said chamber isdivided into an upper and lower portion, the tops of said carriers beingformed to hold divided material and being formed with thinupwardly-extending sagger-holding projections, divided refractoryheat-insulating materlal surrounding said pro ect1ons, and

means for heating the upper portion of said chamber.

7. A sagger carrier for use 1n tunnnel kilns, a tray mounted on saidcarrier in spaced relation thereto, said tray being formed with thininterior sagger-supporting ribs, and divided refractory heat-insulatingmaterial contained in said tray.

8. A carrier having at its top a saggersupporting member and meanscarried by said member for forming a heat-insulating medium between thecarrler and the saggers supported thereby, said means consisting of amaterial formed by heating a mixture of sawdust and refractory materialuntil the refractory material is sintered.

FRANCIS A. J. FITZ GERALD.

